Back in 1961, Carl Sagan wrote a detailed review of what was known about that planet, and also what was speculated by mainstream scientists.

The state of our knowledge of Venus is amply illustrated by the fact that the Carboniferous swamp, the wind-swept desert, the planetary oil field, and the global Seltzer ocean each have their serious proponents, and those planning eventual manned expeditions to Venus must be exceedingly perplexed over whether to send along a paleobotanist, a mineralogist, a petroleum geologist, or a deep-sea diver.

Since that review, several spacecraft have been sent to Venus, and several of them have reported back on conditions there. In 1967, the Russians' Venera 4 landed on that planet and the Americans' Mariner 5 flew by it. The Russian spacecraft's last recorded pressure was 22 bar, while from Mariner 5's signals passing through Venus's atmosphere, the planet's surface pressure is some 75 to 100 bar. Russian planetary scientists claimed that Mariner 4 had reached Venus's surface, while American ones claimed that Venera 4 failed on its way down, at an altitude of around 26 km with a temperature of around 252 C (504 F). Carl Sagan related an argument over that issue with a Russian colleague in his book The Cosmic Connection. Some later Russian spacecraft did reach the planet's surface, and some of them returned pictures of it.

From the Magellan Mission to Venus, it was learned that at least 85% of Venus's surface is covered by lava flows, with the remaining 15% being highly deformed mountain belts. Over 80% of the planet's surface is within 1 km of the planet's mean radius.

So it seems that we should send a volcanologist.

Venus's atmosphere has

Venus's clouds are concentrated sulfuric acid. They extend between altitudes 50 km and 65 km, with a sulfuric-acid haze extending down to 30 km. This sulfuric acid does not reach the surface, because H2SO4 decomposes at 200 - 300 C. But Venus's clouds have Earthlike temperatures and pressures, and I've seen some discussion of sending balloons and airships there.


The Planet Venus by Carl Sagan
Science 24 Mar 1961:
Vol. 133, Issue 3456, pp. 849-858
DOI: 10.1126/science.133.3456.849
The Planet Venus | Science

Venus - Wikipedia

George Adamski and some other 1950's UFO contactees thought that Venus was Earthlike and inhabited by human(oid) entities. Something like Portland, Oregon, a nice city that is clouded over much of the time. I have used that city as an illustration of this hypothesis. Since then, these contactees' defenders have attempted to reconcile those notions with what has been learned about the Solar System since then. Here are what they have proposed:


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